MIT engineers develop ultrasound stickers that can see inside the body

Adhesive patch that produces ultrasound images of the body

MIT engineers have designed an adhesive patch that produces ultrasound images of the body. The tampon-sized device adheres to the skin and can provide continuous ultrasound imaging of internal organs for 48 hours. Credit: Felice Frankel

New tampon-sized ultrasound adhesives provide clear images of the heart, lungs and other internal organs.

When clinicians need live images of a patient’s internal organs, they often turn to ultrasound imaging for a safe, noninvasive window into how the body functions. In order to capture these insightful images, skilled technicians manipulate wands and ultrasound probes to direct sound waves into the body. These waves reflect off each other and are used to produce high resolution images of a patient’s heart, lungs and other deep organs.

Ultrasound imaging currently requires large and specialized equipment available only in hospitals and medical practices. However, a new design developed by[{” attribute=””>MIT engineers might make the technology as wearable and accessible as buying Band-Aids at the drugstore.

The engineers presented the design for the new ultrasound sticker in a paper published on July 28 in the journal Science. The stamp-sized device sticks to skin and can provide continuous ultrasound imaging of internal organs for 48 hours.

To demonstrate the invention, the researchers applied the stickers to volunteers. They showed the devices produced live, high-resolution images of major blood vessels and deeper organs such as the heart, lungs, and stomach. As the volunteers performed various activities, including sitting, standing, jogging, and biking, the stickers maintained a strong adhesion and continued to capture changes in underlying organs.

In the current design, the stickers must be connected to instruments that translate the reflected sound waves into images. According to the researchers, the stickers could have immediate applications even in their current form. For example, the devices could be applied to patients in the hospital, similar to heart-monitoring EKG stickers, and could continuously image internal organs without requiring a technician to hold a probe in place for long periods of time.

Making the devices work wirelessly is a goal the team is currently working toward. If they are successful, the ultrasound stickers could be made into wearable imaging products that patients could take home from a doctor’s office or even buy at a pharmacy.

“We envision a few patches adhered to different locations on the body, and the patches would communicate with your cellphone, where AI algorithms would analyze the images on demand,” says the study’s senior author, Xuanhe Zhao, professor of mechanical engineering and civil and environmental engineering at MIT. “We believe we’ve opened a new era of wearable imaging: With a few patches on your body, you could see your internal organs.”

The study also includes lead authors Chonghe Wang and Xiaoyu Chen, and co-authors Liu Wang, Mitsutoshi Makihata, and Tao Zhao at MIT, along with Hsiao-Chuan Liu of the Mayo Clinic in Rochester, Minnesota.

A sticky question

To image with ultrasound, a technician first applies a liquid gel to a patient’s skin, which acts to transmit ultrasound waves. A probe, or transducer, is then pressed against the gel, sending sound waves through the body that echo internal structures and return to the probe, where the returned signals are translated into visual images.

For patients who require long periods of imaging, some hospitals offer probes attached to robotic arms that can hold a transducer in place without fatigue, but the liquid ultrasound gel will leak out and dry out over time, interrupting long-term imaging.

In recent years, scientists have explored expandable ultrasound probe designs that would provide portable, unobtrusive imaging of internal organs. These designs yielded a flexible array of tiny ultrasound transducers, the idea being that such a device would stretch and conform to a patient’s body.

But these experimental designs produced low-resolution images, in part because of their stretch: as they move with the body, the transducers move relative to each other, distorting the resulting image.

“A portable ultrasound imaging tool would have enormous potential in the future of clinical diagnostics. However, the resolution and imaging time of existing ultrasound patches are relatively low, and they cannot image deep organs,” says Chonghe Wang, who is a graduate student at MIT.

An inside look

By combining a stretchy adhesive layer with a rigid array of transducers, the MIT team’s new ultrasonic sticker produces higher-resolution images over a longer duration. “This combination allows the device to conform to the skin while maintaining the relative location of the transducers to generate clearer, more accurate images.” Wang said.

The device’s adhesive layer consists of two thin layers of elastomer that encapsulate an intermediate layer of solid hydrogel, a primarily water-based material that easily transmits sound waves. Unlike traditional ultrasound gels, the MIT team’s hydrogel is elastic and stretchy.

“The elastomer prevents dehydration of the hydrogel,” says Chen, a postdoctoral fellow at MIT. “Only when the hydrogel is highly hydrated can acoustic waves effectively penetrate and provide high-resolution imaging of internal organs.”

The bottom elastomer layer is designed to stick to the skin, while the top layer adheres to a rigid array of transducers that the team also designed and manufactured. The whole ultrasonic sticker is about 2 square centimeters in diameter and 3 millimeters thick, about the area of ​​a postage stamp.

The researchers subjected the sticker to ultrasound through a battery of tests with healthy volunteers, who wore the stickers on various parts of their bodies, including the neck, chest, abdomen and arms. The stickers stayed attached to their skin and produced clear images of underlying structures for up to 48 hours. During this time, the volunteers performed a variety of activities in the lab, ranging from sitting and standing to jogging, cycling and lifting weights.

From the sticker images, the team was able to observe the change in diameter of major blood vessels when seated compared to when standing. The stickers also captured deeper organ details, such as how the heart changes shape as it moves during exercise. The researchers were also able to observe the stomach expand and then retract as the volunteers drank and then expelled juice from their system. And as some volunteers lifted weights, the team could detect light patterns in underlying muscles, signaling temporary microdamage.

“With imagery, we might be able to capture the timing of a workout before overuse and stop before muscles become sore,” says Chen. “We don’t yet know when that time might be, but now we can provide imaging data that experts can interpret.”

The engineering team is working to make the stickers work wirelessly. They are also developing AI-based software algorithms that can better interpret and diagnose sticker images. Next, Zhao envisions that ultrasound stickers can be packaged and purchased by patients and consumers, and used not only to monitor various internal organs, but also the progression of tumors, as well as the development of fetuses in the womb.

“We imagine we could have a box of stickers, each designed to represent a different location on the body,” Zhao explains. “We believe this represents a breakthrough in wearable devices and medical imaging.”

Reference: “Bioadhesive Ultrasound for Long-Term Continuous Imaging of Various Organs” by Chonghe Wang, Xiaoyu Chen, Liu Wang, Mitsutoshi Makihata, Hsiao-Chuan Liu, Tao Zhou, and Xuanhe Zhao, July 28, 2022, Science.
DOI: 10.1126/science.abo2542

This research was funded, in part, by MIT, the Defense Advanced Research Projects Agency, the National Science Foundation, the National Institutes of Health, and the US Army Research Office through the Institute for Soldier Nanotechnologies at MIT.

Leave a Comment